Accumulated Other Comprehensive Income (Balance of and Changes in Each Component of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					$ 2,108,902		$ 1,618,153
Other comprehensive income (loss) before reclassifications					(1,012,727)
Amounts reclassified from AOCI					3,826
Net current-period other comprehensive income (loss)	(82,133)		352,449		(1,008,901)		533,494
Change in component during the period							533,494
Balance, End of Period	1,100,001		2,151,647		1,100,001		2,151,647
Accumulated Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					267,475		229,795
Other comprehensive income (loss) before reclassifications					(75,798)
Amounts reclassified from AOCI					0
Net current-period other comprehensive income (loss)					(75,798)
Change in component during the period							43,463
Balance, End of Period	191,677		273,258		191,677		273,258
Unrealized Appreciation Of Securities [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					1,877,657	[1]	1,419,318	[1]
Other comprehensive income (loss) before reclassifications					(936,847)	[1]
Amounts reclassified from AOCI					1,527	[1]
Net current-period other comprehensive income (loss)					(935,320)	[1]
Change in component during the period							488,194	[1]
Balance, End of Period	942,337	[1]	1,907,512	[1]	942,337	[1]	1,907,512	[1]
Pension And Postretirement Benefits [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance, Beginning of Period					(36,230)		(30,960)
Other comprehensive income (loss) before reclassifications					(82)
Amounts reclassified from AOCI					2,299
Net current-period other comprehensive income (loss)					2,217
Change in component during the period							1,837
Balance, End of Period	$ (34,013)		$ (29,123)		$ (34,013)		$ (29,123)

[1] Includes cash flow hedges. See Note 5 - “Derivative Instruments” for additional information on cash flow hedges.